This application claims the priority of German patent document 10 2004 032 985.0, filed Jul. 8, 2004 (PCT International Application No. PCT/EP2005/007110, filed Jul. 1, 2005), the disclosure of which is expressly incorporated by reference herein.
The invention relates to a motor vehicle having a preventatively acting safety system in which safety devices are activated based on an evaluation of a detected driving situation.
It is known to equip motor vehicles, such as passenger cars, with active and passive safety devices that allow the driver to better control his vehicle in critical situations, and thus to prevent the vehicle's possibly being involved in an accident. Safety devices of this type also help to reduce the severity of an accident in the event of a collision.
Safety systems which take preventative action even before a possible collision and use a so-called pre-crash phase (that is, a period of time starting from when detection systems in the vehicle detect a high probability of collision until the actual impact) to increase occupant protection by means of additional safety measures and thus reduce the severity of an accident, are known as preventatively acting safety systems. Safety systems of this type use information which is provided by various sensor devices of the motor vehicle to identify possible accident situations. Such sensor devices may include, for example, a constituent part of an electronic driving stabilizing program and/or a constituent part of a distance sensor system. Conclusions are then drawn about a possible impact on the basis of the identified situation, and corresponding measures are initiated to prepare the vehicle and occupant restraint systems for the imminent accident.
German patent document DE 101 21 386 C1 discloses a preventatively acting safety system in which driving state data are detected by means of a sensor system. A reversible occupant protection system can be activated and thus moved to the active position before a collision occurs. A safety system of this type is also called a PRE-SAFE system (registered trademark). A sensor system monitors the driving state data for any possible emergency braking, oversteering and understeering operations, and activates the occupant protection system if such condictions are detected at a time when a minimum speed is exceeded. The sensor system for detecting the driving state data may comprise a steering angle sensor, a pedal travel sensor, a brake pressure sensor, a wheel rotational speed sensor, an acceleration sensor and a yaw rate sensor.
The critical limit range is found to vary greatly in a subjective manner, depending on the speed at which the vehicle is traveling or the accelerations to which it is subjected. Therefore, understeer or oversteer is better tolerated at low speeds or low accelerations than at high speeds or accelerations in the longitudinal or lateral direction.
The occupant protection system known from German patent document DE 101 21 386 C1 is always activated at the same triggering threshold value, and therefore has a triggering behavior which is found to be subjectively sensitive at low vehicle speeds or accelerations and comparatively insensitive at high vehicle speeds or accelerations.
One object of the present invention is to provide a motor vehicle having a preventatively acting safety system of the type described above, which provides a triggering behavior of safety devices for occupants which is better matched to the current driving state and to the subjective sensing of driving-critical situations.
This and other objects and advantages are achieved by the preventatively acting safety system according to the invention, in which the triggering threshold value is adapted for a lateral dynamics-critical driving situation as a function of total vehicle acceleration and/or vehicle speed. The invention thus makes it possible to adapt the triggering behavior of an occupant and/or partner protection system which is in the form of a preventatively acting safety system, as a function of the coefficient of friction. It is possible, in particular, for the triggering thresholds to be applied separately for high and for low coefficients of friction.
The preventatively acting safety system according to the invention therefore means that the triggering threshold value which is associated with a lateral dynamics-critical driving situation, (e.g., a state of understeer or a state of oversteer) can be reduced in the case of a high coefficient of friction. This in turn increases the number of activations, particularly at high vehicle speeds, compared to a conventional preventatively acting safety system, and thus may possibly increase acceptance of the preventatively acting safety system by a user of the motor vehicle.
The preventatively acting safety system according to the invention, also makes it possible to adapt to the sense of danger felt by the vehicle user. The user generally feels safe at low vehicle speeds and low coefficients of friction, so that the triggering threshold value can assume a higher value. At high vehicle speeds and high coefficients of friction, the subjective sense of danger is generally more pronounced, so that the triggering threshold value then advantageously assumes a lower value.
The safety devices which are actuated when the triggering threshold value is exceeded may include, for example, a belt tensioning system, an airbag system, an electrical seat adjusting device, a cushion whose shape, size and/or position can be adjusted, or other vehicle components which can be adjusted electrically, hydraulically or pneumatically with a view to increasing safety.
The driving situation detection device may comprise a sensor system of various designs which is equipped, for example, with a steering angle sensor, a pedal travel sensor, a brake pressure sensor, a wheel rotational speed sensor, an acceleration sensor, a yaw rate sensor and/or a distance sensor.
The data evaluation device of the preventatively acting safety system according to the invention may be a data processing device of a driving stabilizing system of the motor vehicle which is often present in any case, particularly in modern motor vehicles. Alternatively, it is of course possible to employ a separate data processing device too.
In order to identify a lateral dynamics-critical driving situation (for example, “understeer”, in which the radius of the desired path prescribed by the steering angle is less than the radius of the path actually traveled by the vehicle, or “oversteer”, in which the radius of the desired path prescribed by the steering angle is greater than the radius of the path actually traveled), the total vehicle acceleration (which is found by adding the longitudinal and lateral vehicle acceleration determined by acceleration sensors and/or a yaw sensor) is expediently analyzed. If the analysis shows that the triggering threshold value which varies as a function of the coefficient of friction is exceeded, the data evaluation device outputs a collision plausibility, so that the safety devices which interact with the preventatively acting safety system can be activated and conditioned in accordance with the possible accident situation.
The preventatively acting safety system according to the invention preferably represents a reversible occupant protection system which can be moved from an initial state to an operative state and back from the operative state to its initial state again a number of times.
In one preferred embodiment of the invention, the triggering threshold value is dynamically adapted at least substantially continuously (that is, smoothly). It is therefore possible to adapt the triggering threshold value as a function of the coefficient of friction over the entire speed range of the motor vehicle.
Starting from a threshold value at a low vehicle speed and a low total vehicle acceleration (that is, in the case of a low coefficient of friction) it is expedient to reduce the triggering threshold value by up to approximately up to 50% as the vehicle speed and/or the total vehicle acceleration increase. This ensures that the preventatively acting safety system always responds in a manner which is matched to the driving situation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.